The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Today, maps of geographic regions may be displayed by software applications running on a wide variety of devices, including mobile phones, car navigation systems, hand-held global positioning system (GPS) units, and computers. Depending on the application and/or user preferences, maps may display topographical data, street data, urban transit information, traffic data, etc. Further, some applications display maps in an interactive mode, so that a user may operate various controls (radio buttons, scrollbars, etc.) to change the zoom level or pan the “camera” to a new location, for example. A user in some cases also may select or unselect the display of certain information. For example, the user may operate the appropriate control to turn on the display of bicycle trails.
To render a map image, a client device typically receives raster images from a dedicated server. For example, a map server may operate on the Internet and provide images in a Portable Network Graphics (PNG) format to various client devices for the specified geographic regions. While raster images are relatively easy to render at a client device, raster image data typically requires a large amount of storage space for a comprehensive map. Also, it is difficult to efficiently manipulate raster images at a client device. For example, to zoom in on a selected region, either new raster image data is retrieved from the server, or the available raster image data is enlarged with a noticeable loss in quality. Further, to change the visual properties of a map image, the client device must request new raster image data from the map server.